If I recall correctly (and I could be wrong), Aya Brea's wedding dress was totally white back in that original wedding scene trailer for The 3rd Birthday. But it's gotten a bit of color in the game's latest CG work, which debuted on the cover of this week's Dengeki PlayStation:

The magazine has a 10 page feature on the game with a staff interview, all of which was summarized at this blog.

While Aya's wedding dress hasn't been confirmed as one of Aya's costumes, Dengeki does have the first word another costume: Santa Soldier. This Santa outfit has a revealing skirt and long boots, and even gives Aya a cute little present bag hanging off her shoulders.

The interview reveals that the game will have around 10 costumes total, some of which have yet to be announced.